This invention relates generally to fluid flowmeters and, more particularly, to insertion-type fluid flowmeters that can be extended through the wall of a conduit and that include a rotor configured to rotate at a rate that varies with fluid flow rate.
Fluid flowmeters of this particular kind typically mount the rotor at the end of a strut that projects radially into the conduit, through an opening formed in the conduit wall. The rotor can take the form of a paddle wheel, rotatable about an axis transverse to the direction of fluid flow, or alternatively can take the form of a multi-bladed turbine or propeller, rotatable about an axis aligned with the direction of fluid flow. In either case, permanent magnets can be embedded within the tips of the individual paddles or blades, for sensing by a sensor located within the strut, to produce a measurement of fluid flow rate.
In the case of flowmeters incorporating propeller-type rotors, accuracy and sensitivity generally can be enhanced if the rotor is made to rotate about an axis substantially aligned with the conduit's centerline and also if the rotor's circular sweep area is made to be as large as possible. Ordinarily, this can be achieved only if the opening in the wall of the conduit is quite large, because the opening must be sized to allow insertion and removal of the strut and rotor. This can lead to difficulties in sealing the opening after the strut and rotor have been inserted.
Fluid flowmeters of this kind have utility in measuring the flow rates of both liquids and gases, and particularly liquids flowing through large pipes. Such pipes can vary in diameter to as high as 400 mm. This large size makes even more difficult the sealing problems mentioned above.
It should, therefore, be appreciated that there is a need for an improved insertion-type fluid flowmeter incorporating a rotor configured to sweep through a circular area of diameter substantially larger than the maximum dimension of the opening in the conduit. It should also be appreciated that there is a need for an improved flowmeter of this kind, configured for convenient replacement of the strut and rotor, and fuither configured for convenient adjustment of position of the rotor's rotation axis within the conduit. The present invention fulfills these needs and provides further related advantages.